β-Lapachone (β-lap) is a natural product isolated from the lapacho tree in South America. Beta lapachone is a potent cytotoxic anticancer agent with antitumor activity against a variety of human cancer cells, including drug resistant cell lines. Recent studies uncovering its unique mechanism of action have raised considerable interests for the clinical evaluation of this agent. β-Lap kills tumor cells containing NADP(H):quinone oxidoreductase 1 (NQO1), an enzyme overexpressed in a number of tumors, including breast, colon, and lung cancers (Bentle, M. S., Reinicke, K. E., Dong, Y., Bey, E. A., and Boothman, D. A. (2007) Nonhomologous End Joining Is Essential for Cellular Resistance to the Novel Antitumor Agent β-Lapachone. Can. Res. 67, 6936-6945), prostate (Dong, Y., Chin, S. F., Blanco, E., Bey, E. A., Kabbani, W., Xie, X. J., Bornmann, W. G., Boothman, D. A., and Gao, J. (2009) Intratumoral Delivery of -Lapachone via Polymer Implants for Prostate Cancer Therapy. Clin. Can. Res. 15, 131-139), pancreas (Ough, M., Lewis, A., Bey, E. A., Gao, J., Ritchie, J. M., Bornmann, W., Boothman, D. A., Oberley, L. W., and Cullen, J. J. (2005) Efficacy of beta-lapachone in pancreatic cancer treatment: exploiting the novel, therapeutic target NQO1. Can. Bio. Ther. 4, 95-102), and non-small cell lung cancers (NSCLC) (Bey, E. A., Bentle, M. S., Reinicke, K. E., Dong, Y., Yang, C. R., Girard, L., Minna, J. D., Bornmann, W. G., Gao, J., and Boothman, D. A. (2007) An NQO1- and PARP-1-mediated cell death pathway induced in non-small-cell lung cancer cells by beta-lapachone. Proc. Natl. Acad. Sci. USA 104, 11832-11837).
Upon NQO1 bioactivation, β-lap undergoes a futile cycle resulting in the rapid formation of reactive oxygen species (ROS) and depletion of NAD(P)H. Each mole of β-lap can produce 120 moles of H2O2 and other ROS, which causes DNA single-strand breaks, hyper-activation of poly(ADP-ribose) of polymerase-1, loss of NAD+ and ATP, and irreversible cell death (Tagliarino, C., Pink, J. J., Dubyak, G. R., Nieminen, A. L., and Boothman, D. A. (2001) Calcium is a key signaling molecule in beta-lapachone-mediated cell death. J. Biol. Chem. 276, 19150-19159). Cell death by β-lap is independent of p53, cell cycle and Rb status, and no drug resistance has been found. At optimal concentrations and duration of exposure to cells, beta lap causes DNA damage, inhibits DNA repair and induces programmed cell death.
Despite the unique mechanism of action, selectivity and potency, preclinical and clinical evaluations of β-lap are currently limited. Free β-lap has a low aqueous solubility of 0.038 mg/ml, which limits direct injection in patients. Hydroxylpropyl β-cyclodextrin has been used to effectively solubilize β-lap by the formation of inclusion complex. The low binding affinity (binding constant=1.1×103M−1) (Wang, F., Blanco, E., Ai, H., Boothman, D. A., and Gao, J. (2006) Modulating β-lapachone release from polymer millirods through cyclodextrin complexation. J. Pharm. Sci. 95, 2309-2319), however, resulted in the rapid dissociation of the complex, fast renal clearance and short half-life (0.4 hour) in blood, far shorter than the minimally required duration of drug exposure needed to achieve cytotoxicity. In addition, hemolysis and hemoglobinemia were found as the major side effects, causing the withdrawal of the complex (ARQ501) from clinical trials. A better delivery strategy for β-lap is greatly needed.
Polymeric micelles are supramolecular core-shell nanoparticles self-assembled from amphiphilic block copolymers. Micelle formations containing a drug have been described. Kim, D. W., Kim, S. Y., Kim, H. K., Kim, S. W., Shin, S. W., Kim, J. S., Park, K., Lee, M. Y., and Heo, D. S. (2007) Multicenter phase II trial of Genexol-PM, a novel Cremophor-free, polymeric micelle formulation of paclitaxel, with cisplatin in patients with advanced non-small-cell lung cancer. Ann Oncol 18, 2009-14).
The lower pH of tumor extracellular and tumor cell late endosomal/lysosomal (pH 4.0-5.0) compared to normal tissue cells and bloodstream (Vaupel, P., Kallinowski, F., and Okunieff, P. (1989) Blood flow, oxygen and nutrient supply, and metabolic microenvironment of human tumors: a review. Can. Res. 49, 6449-65; Ulbrich, K., and Subr, V. (2004) Polymeric anticancer drugs with pH-controlled activation. Adv Drug Deliv Rev 56, 1023-50; Ganta, S., Devalapally, H., Shahiwala, A., and Amiji, M. (2008) A review of stimuli-responsive nanocarriers for drug and gene delivery. J. Controlled. Release 126, 187-204) can facilitate pH responsive delivery of anticancer drugs by polymeric micelles; the polymeric micelles may keep integrity in the bloodstream pH but release their contents when exposed to tumor extracellular pH or late endosome/lysosome pH. However, the release of contents will be retarded or hindered (Griset, A. P., Walpole, J., Liu, R., Gaffey, A., Colson, Y. L., and Grinstaff, M. W. (2009) Expansile nanoparticles: synthesis, characterization, and in vivo efficacy of an acid-responsive polymeric drug delivery system. J. Am. Chem. Soc. 131, 2469-2471) if micelle cores are not sensitive enough to outer pH stimuli.
One type of pH sensitive polymeric micelles are polymer chains with ionizable groups which act as hydrophilic or hydrophobic parts of a polymer at various water pH. The polymer is soluble when it is ionized, but it is insoluble when it is deionized, which causes a reversible soluble-insoluble transition to occur as the hydrophobicity of the polymer changes. An acidic group such as a carboxyl group becomes ionized at pH values above the pKa and deionized at pH values below the pKa, whereas a basic group such as an amine becomes deionized at pH values below the pKb and ionized at pH values above pKb.
Various micelle systems have been described. See e.g.:    Sutton, D., Nasongkla, N., Blanco, E., and Gao, J. (2007) Functionalized micellar systems for cancer targeted drug delivery. Pharm. Res. 24, 1029-1046;    Bae, Y., Jang, W.-D., Nishiyama, N., Fukushima, S., and Kataoka, K. (2005) Multifunctional polymeric micelles with folate-mediated cancer cell targeting and pH-triggered drug releasing properties for active intracellular drug delivery. Mol Biosyst 1, 242-50;    Bae, Y., Nishiyama, N., Fukushima, S., Koyama, Yasuhiro, M., and Kataoka, K. (2005) Preparation and biological characterization of polymeric micelle drug carriers with intracellular pH-triggered drug release property: tumor permeability, controlled subcellular drug distribution, and enhanced in vivo antitumor efficacy. Bioconjug Chem 16, 122-30;    Vetvicka, D., Hruby, M., Hovorka, O., Etrych, T., Vetrik, M., Kovar, L., Kovar, M., Ulbrich, K., and Rihova, B. (2009) Biological evaluation of polymeric micelles with covalently bound doxorubicin. Bioconjugate Chem. 20, 2090-2097;    Jung, J., Lee, I.-H., Lee, E., Park, J., and Jon, S. (2007) pH-sensitive polymer nanospheres for use as a potential drug delivery vehicle. Biomacromolecules 8, 3401-7;    Lee, E. S., Shin, H. J., Na, K., and Bae, Y. H. (2003) Poly(L-histidine)-PEG block copolymer micelles and pH-induced destabilization. J Control Release 90, 363-74;    Lee, E. S., Na, K., and Bae, Y. H. (2005) Doxorubicin loaded pH-sensitive polymeric micelles for reversal of resistant MCF-7 tumor. J Control Release 103, 405-18;    Kim, D., Lee, E. S., Park, K., Kwon, I. C., and Bae, Y. H. (2008) Doxorubicin loaded pH-sensitive micelle: antitumoral efficacy against ovarian A2780/DOXR tumor. Pharm. Res. 25, 2074-82;    Jung, J., Lee, I.-H., Lee, E., Park, J., and Jon, S. (2007) pH-sensitive polymer nanospheres for use as a potential drug delivery vehicle. Biomacromolecules 8, 3401-7.    Methacrylate polymers are described in: Butun, V., Armes, S. P., and Billingham, N. C. (2001) Synthesis and aqueous solution properties of near-monodisperse tertiary amine methacrylate homopolymers and diblock copolymers. Polymer 42, 5993-6008.
Acylhydrazone and ketal linkers have been reported. See, e.g.:    T. Nakanishi et al. (2001); Development of the polymer micelle carrier system for doxorubicin. J. Controlled. Release 74, 295-302;    Bae, Y., Fukushima, S., Harada, A., and Kataoka, K. (2003) Design of environment-sensitive supramolecular assemblies for intracellular drug delivery: polymeric micelles that are responsive to intracellular pH change. Angew. Chem. Int. Ed. Engl. 42, 4640-4643;    Alani, A. W. G., Bae, Y., Rao, D. A., and Kwon, G. S. (2010) Polymeric micelles for the pH-dependent controlled, continuous low dose release of paclitaxel. Biomaterials 31, 1765-1772;    Griset, A. P., Walpole, J., Liu, R., Gaffey, A., Colson, Y. L., and Grinstaff, M. W. (2009) Expansile nanoparticles: synthesis, characterization, and in vivo efficacy of an acid-responsive polymeric drug delivery system. J. Am. Chem. Soc. 131, 2469-2471.    Sy, J. C., Phelps, E. A., Garcia, A. J., Murthy, N., and Davis, M. E. (2010) Surface functionalization of polyketal microparticles with nitrilotriacetic acid-nickel complexes for efficient protein capture and delivery. Biomaterials 31, 4987-4994;    Seshadri, G., Sy, J. C., Brown, M., Dikalov, S., Yang, S. C., Murthy, N., and Davis, M. E. (2010) The delivery of superoxide dismutase encapsulated in polyketal microparticles to rat myocardium and protection from myocardial ischemia-reperfusion injury. Biomaterials 31, 1372-1379; and    Heffernan, M. J., and Murthy, N. (2005) Polyketal nanoparticles: a new pH-sensitive biodegradable drug delivery vehicle. Bioconjugate Chem. 16, 1340-1342).
What is needed are improved compositions and methods for delivery of β-lap.
All publications, patent applications, and patents cited in this specification are herein incorporated by reference as if each individual publication, patent application, or patent were specifically and individually indicated to be incorporated by reference. In particular, all publications cited herein are expressly incorporated herein by reference for the purpose of describing and disclosing compositions and methodologies which might be used in connection with the invention.